Diffusion dark current in front-illuminated CCDs and CMOS image sensors

The dark current that arises due to diffusion from the bulk is assuming a more important role now that CCD and CMOS image sensors have found their way into consumer electronics which must be capable of operating at elevated temperatures. Historically this component has been estimated from the diffusion related current of a diode with an infinite substrate. This paper explores the effect of a substrate of finite extent beneath the collecting volume of the pixel for a front-illuminated device and develops a corrected expression for the diffusion related dark current. The models show that the diffusion dark current can be much less than that predicted by the standard model.